1. Field of the Invention
The present invention relates generally to the art of hydraulic pressure control valves and methods for assembling the same. More specifically, the present invention relates to an improved hydraulic modulated pressure control valve, used in connection with a device requiring a controlled pressure, wherein the mechanism by which the inflow of hydraulic fluid is modulated to more faithfully transmit the pulses of the control mechanism to the controlled pressure device. Additionally, the solenoid of the improved valve is adjustable to provide varying performance standards. Finally, a method for assembling the improved valve is shown.
2. Description of Related Areas of Art
Modulating pressure control valves are well known in the hydraulic valve art. A good example of such a valve is shown in U.S. Pat. No. 4,538,644 entitled "Pressure Regulator" issued to Knutson, et al on Sept. 3, 1985. In the preferred embodiment of that invention shown in FIG. 1, a modulator 24 controls the access of hydraulic fluid to the cylinder 60. The plunger 54 reduces and increases the clearance through orifice 48 to thereby control pressure in chamber 16.
Another similar valve is shown in U.S. Pat. No. 4,576,200 entitled "Hydraulic Pressure Reducing Control Valve" issued to Janecke, et al on Mar. 18, 1986. That valve also utilizes a modulator or solenoid 24 which controls hydraulic fluid flow from a pump 11. Pressure from the fluid allowed into chamber 36 by plunger 28 moves a spool valve 50 into a position in which the fluid can be supplied to a device requiring a controlled pressure.
In addition to the Knutson and Janecke devices, an earlier generation of the present invention used a similar configuration and operation. Several differences noted below exist between that valve and the other designs. It is known in the art that a solenoid can be used to control the opening and closing of a valve by magnetically moving a disc covering an aperture away from that aperture against a force from a spring or other biasing element. The magnetic attraction can be created by a fixed solenoid which generates a magnetic field. Problems occur with the movement of the disc portion of the valve due to residual magnetism after the solenoid field is turned off. Furthermore, the natural adhesion that occurs between solid planar surfaces and fluids can prevent ideal operation of the valve, especially in cold weather. In addition, the characteristics of the magnetic field were unable to be changed in such prior generation valve and no adjustment of performance specifications of the disc movement and output characteristics of the valve were possible. The present invention has greatly minimized the problems encountered in construction and operation of such valves.